1. Field of the Invention
The present invention relates to a taking lens for an underwater camera and more particularly to a taking lens for an underwater camera capable of close-up photography.
2. Related Background Art
In performing close-up photography underwater, there has been conventionally used an underwater camera equipped with a close-up photographing device whose visual field frame is equivalent to that of a close-up lens or a single-lens reflex camera equipped with a micro lens and contained in an underwater housing.
However, in the former case, it is difficult to ascertain the taking range and its magnification is not so high. Further, aberration corrections cannot be effected sufficiently. Also, in the latter case, various aberrations occur in the window of the housing, causing the image forming performance to be lowered.
Recently, a single-lens reflex type underwater camera and an underwater specialized lens are likely to be put to practical use. As such an underwater specialized lens, U.S. Ser. No. 855,165 discloses an embodiment having a field angle equivalent to a lens with a rear focal length of approximately 50 mm underwater when converted to the 35 mm size film and an embodiment having a field angle equivalent to a lens with a rear focal length of approximately 105 mm in the same condition.
However, in the former embodiment, it is impossible to take a working distance long in the close-up photography, which is disadvantageous in terms of illumination to a subject.
Also, in the latter embodiment, its structure is the retrofocus type, so the optical system is liable to become large.